Unable to restore due to backup archive cryptography key error

Overview

This article describes a known issue in which versions of the CrashPlan app that use Blowfish encryption are unable to restore files that were backed up from a device using AES encryption. This typically only happens if a user backs up files from a device with a new version of the CrashPlan app and then attempts to restore the files to a device with an older version of the CrashPlan app.

Affects

CrashPlan apps with AES encryption enabled. AES encryption is available in version 4.2 and later of CrashPlan PROe and 4.6 and later of CrashPlan for Small Business (previously CrashPlan PRO).

Diagnosing

This issue occurs only under the following circumstances:

A CrashPlan device backs up with AES encryption.

The user signs in to a device using a version of the CrashPlan app that does not support AES encryption.

Attempting to restore files backed up with AES encryption displays the message, "Unable to restore due to a backup archive cryptography key error."

This results in the user being unable to restore previously backed up files.